None of the official methods worked for me (not even ;)). So I ended up going the super manual route (mostly copying and ).
$ sudo apt-get install lshw
$ sudo lshw
description: Computer
product: Raspberry Pi 4 Model B Rev 1.4
serial: 10000000d5e618a2
width: 64 bits
; OK, it's 64bits
; Get Arm64 download URL from https://dotnet.microsoft.com/download/dotnet/5.0
$ mkdir temp && cd temp
$ curl [URL] --output [FILENAME]
$ mkdir $HOME/dotnet
$ sudo tar zxf [FILENAME] -C $HOME/dotnet/
$ sudo ln -s $HOME/dotnet/dotnet /usr/local/bin
$ dotnet --version
5.0.203
; or whatever version you downloaded
; Now we need to add it to PATH. Add the exports
$ sudo nano ~/.bashrc
export DOTNET_ROOT=$HOME/dotnet
export PATH=$PATH:$HOME/dotnet
export PATH=$PATH:$HOME/.dotnet/tools
; then Ctrl+X to save and exit. finally, load the new exports
$ source ~/.bashrc
